A child-parent referential integrity (“RI”) constraint between a parent table and a child table requires that a foreign key value in each child table row have a matching primary key value in a parent table row. In a non-temporal database, some forms of join can be simplified if there is RI between the tables being joined. In some cases, the parent table can be removed from a query involving a join between a child table and a parent table. Such simplifications are a challenge for joins involving temporal tables.